On the Air: Urban Trees Cool Chicago, Save $44 Million a Year

What’s cool depends on who you’re asking. James Dean was definitely cool, Mike Posner not so much, and tree hugging—well, again, it depends who you are asking.

Today on Worldview, Jerome McDonnell and I explored the topic of how trees cool our homes, our cities, and our planet. We invited Robert Fahey PhD, an expert in forest ecosystems at the Morton Arboretum, to tell us about the amazing things that trees do as well as the threats to trees caused by the warming planet.

As many people know, carbon dioxide (CO2) occurs in the atmosphere naturally as part of the cycle of life on earth. But excess CO2 emitted into the atmosphere causes planetary temperatures to rise. Fahey explains that forests and trees absorb much of that carbon from the atmosphere, store it in their wood, and emit oxygen in return, making forests extremely important for mitigating climate change.

He described how forests around the world, including in Borneo, the Amazon, and Siberia, are suffering the impacts of global temperature rise, such as fire, severe storm damage, and drought. In the Midwest and Eastern U.S., many of our native trees, such as oaks, are hearty in a broad range of temperatures but they remain vulnerable to insects and pathogens that thrive in warmer climates. These living threats include emerald ash borer in the Midwest and the mountain pine beetle, which is devastating forests in the Mountain West. Fahey says that the management policy in large forests is to let trees adapt naturally. But in urban settings we can select trees that are more resilient to various urban stresses.

In cities such as Chicago, he says, trees are “extremely important for reducing energy costs and cooling the city.” He said a recent study “estimated that the urban forests in the Chicago region reduce energy costs by about $44 million per year,” in addition to reducing the amount of carbon released into the atmosphere due to less fossil fuel burned than would have been used to create that energy.

Listen to the podcast of our conversation for the whole story and to learn about the global feedback cycle that includes trees and CO2. For a deeper dive, read the myth and science blog.